Economic impact of potential CYP450 pharmacokinetic drug-drug interactions among chronic low back pain patients taking opioids

Health care system costs related to potentially inappropriate medication use involving opioids in older adults in Canada

BACKGROUND

Older adults are at risk of potentially inappropriate medication use given polypharmacy, multimorbidity, and age-related changes, which contribute to the growing burden associated with opioid use. The objective of this study was to estimate the costs of health service utilization attributable to opioid use and potentially inappropriate medication use involving opioids in older adults in a public health care system.

METHODS

The sample included 1201 older adults consulting in primary care, covered by the public drug plan, without a cancer diagnosis and opioid use in the year before interview. Secondary analyses were conducted using two data sources: health survey and provincial administrative data. Health system costs included inpatient and outpatient visits, physician billing, and medication costs. Unit costs were calculated using annual financial and activity reports from 2013-2014, adjusted to 2022 Canadian dollars. Opioid use and potentially inappropriate medication use involving opioids were identified over 3 years. Generalized linear models with gamma distribution were employed to model 3-year costs associated with opioid use and potentially inappropriate medication use involving opioids. A phase-based approach was implemented to provide descriptive results on the costs associated with each phase: i) no use, ii) opioid use, and iii) potentially inappropriate medication use involving opioids.

RESULTS

Opioid use and potentially inappropriate medication use involving opioids were associated with adjusted 3-year costs of $2,222 (95% CI: $1,179-$3,264) and $8,987 (95% CI: $7,370-$10,605), respectively, compared to no use. In phase-based analyses, costs were the highest during inappropriate use.

CONCLUSIONS

Potentially inappropriate medication use involving opioids is associated with higher costs compared to those observed with opioid use and no use. There is a need for more effective use of health care resources to reduce costs for the health care system.

Quantifying the economic burden of unintended pregnancies due to drug–drug interactions with hormonal contraceptives from the United States payer perspective

Background: In the United States of America (USA), nearly 10 million women use oral contraceptives (OCs). Concomitant administration of certain medications can result in contraceptive failure, and consequently unintended pregnancies due to drug–drug interactions (DDIs). The objective of this analysis was to estimate the economic impact of unintended pregnancies due to DDIs among women of reproductive age using an OC alone or in combination with an enzyme inducer co-medication in the USA from a payer perspective. Methods: A Markov model using a cohort of 1,000 reproductive-age women was developed to estimate costs due to contraceptive failure for OC alone versus OC with concomitant enzyme inducer drugs. All women were assumed to begin an initial state, continuing until experiencing an unintended pregnancy. Unintended pregnancies could result in birth, induced abortion, spontaneous abortion, or ectopic pregnancy. The cohort was analyzed over a time horizon of 1 year with a cycle length of 1 month. Estimates of costs and probabilities of unintended pregnancy outcomes were obtained from the literature. Probabilities from the Markov cohort trace was used to estimate number of pregnancy outcomes. Results: On average, enzyme inducers resulted in 20 additional unintended pregnancies with additional unadjusted and adjusted costs median (range) of USD136,304 (USD57,436–USD320,093) and USD65,146 (USD28,491–USD162,635), respectively. The major component of the direct cost is attributed to the cost of births. Considering the full range of events, DDIs with enzyme inducers could result in 16–25 additional unintended pregnancies and total unadjusted and adjusted costs ranging between USD46,041 to USD399,121 and USD22,839 to USD202,788 respectively. Conclusion: The direct costs associated with unintended pregnancies due to DDIs may be substantial and are potentially avoidable. Greater awareness of DDI risk with oral contraceptives among payers, physicians, pharmacists and patients may reduce unintended pregnancies in at-risk populations.

Use of Drug Claims Data and a Medication Risk Score to Assess the Impact of CYP2D6 Drug Interactions among Opioid Users on Healthcare Costs

Cytochrome P450 2D6 (CYP2D6) activity is highly variable due to several factors, including genetic polymorphisms and drug-drug-gene interactions. Hydrocodone, oxycodone, codeine, and tramadol the most commonly prescribed CYP2D6-activated opioids for pain. However, the co-administration of CYP2D6 interacting drugs can modulate CYP2D6-medicated activation of these opioids, affecting drug analgesia, effectiveness, and safety, and can impact healthcare costs. A retrospective, observational cohort analysis was performed in a large (n = 50,843) adult population. This study used drug claims data to derive medication risk scores and matching propensity scores to estimate the effects of opioid use and drug-drug interactions (DDIs) on medical expenditures. 4088 individuals were identified as opioid users; 95% of those were prescribed CYP2D6-activated opioids. Among those, 15% were identified as being at risk for DDIs. Opioid users had a significant increase in yearly medical expenditure compared to non-opioid users ($2457 vs. $1210). In matched individuals, average healthcare expenditures were higher for opioid users with DDIs compared to those without DDIs ($7841 vs. $5625). The derived medication risk score was higher in CYP2D6 opioid users with interacting drug(s) compared to no DDI (15 vs. 12). Higher costs associated with CYP2D6 opioid use under DDI conditions suggest inadequate CYP2D6 opioid prescribing practices. Efforts to improve chronic opioid use in adults should reduce interacting drug combinations, especially among patients using CYP2D6 activated opioids.

Effect of nationwide concurrent drug utilization review program on drug-drug interactions and related health outcome

BACKGROUND

A computerized drug utilization review (DUR) program has provided physicians and pharmacists with alerts on drug-drug interactions (DDIs), drug-age precautions and therapeutic duplication in Korea since 2010.

OBJECTIVE

The purpose of this study was to evaluate the impact of the DUR program on health outcomes associated with DDIs.

METHODS

An uncontrolled before-after study was performed to investigate the impact of the nationwide DUR program on DDIs and related health outcomes. The study population consisted of people who used two types of DDI pairs before DUR implementation (from January 2009 to December 2010) and post-DUR implementation (from January 2012 to December 2013); (i) benzodiazepines with concurrent use of metabolic enzyme inhibitors and (ii) QTc (heart-rate corrected QT interval) prolongation agents. The main outcome measures were all-cause and cause-specific hospitalization admissions or emergency department (ED) visits.

RESULTS

This study included 107 874 people who used benzodiazepines with enzyme inhibitors and 8489 who received co-medication of QTc prolongation agents. For patients receiving a combination of benzodiazepines and enzyme inhibitors, both all-cause hospitalization and cause-specific hospitalization decreased after DUR implementation, from 43.2% to 41.7% and from 4.6% to 4.5% (adjusted odds ratio [OR] = 0.96; 95% confidence interval (CI), 0.93-0.98; OR = 0.89, 95% CI = 0.84-0.99, respectively). For patients receiving co-medication of QTc prolongation agents, all-cause hospitalization (54.2%) was lower than before (54.9%) (OR = 0.87, 95% CI = 0.79-0.96), but no significant change was found for cause-specific hospitalization and ED visits.

CONCLUSION

Implementation of a DUR program may reduce the adverse health outcomes posed by DDIs in patients on combination of benzodiazepines and enzyme inhibitors potentially QTc-prolongation agents.

Opioids, Polypharmacy, and Drug Interactions: A Technological Paradigm Shift Is Needed to Ameliorate the Ongoing Opioid Epidemic

Polypharmacy is a common phenomenon among adults using opioids, which may influence the frequency, severity, and complexity of drug–drug interactions (DDIs) experienced. Clinicians must be able to easily identify and resolve DDIs since opioid-related DDIs are common and can be life-threatening. Given that clinicians often rely on technological aids—such as clinical decision support systems (CDSS) and drug interaction software—to identify and resolve DDIs in patients with complex drug regimens, this narrative review provides an appraisal of the performance of existing technologies. Opioid-specific CDSS have several system- and content-related limitations that need to be overcome. Specifically, we found that these CDSS often analyze DDIs in a pairwise manner, do not account for relevant pharmacogenomic results, and do not integrate well with electronic health records. In the context of polypharmacy, existing systems may encourage inadvertent serious alert dismissal due to the generation of multiple incoherent alerts. Future technological systems should minimize alert fatigue, limit manual input, allow for simultaneous multidrug interaction assessments, incorporate pharmacogenomic data, conduct iterative risk simulations, and integrate seamlessly with normal workflow.

Genetics and Opioids: Towards More Appropriate Prescription in Cancer Pain

Opioids are extensively used in patients with cancer pain; despite their efficacy, several patients can experience ineffective analgesia and/or side effects. Pharmacogenetics is a new approach to drug prescription based on the “personalized-medicine” concept, i.e., the ability of tailoring treatments to each individual’s genetic/genomic profile. Pharmacogenetics aims to identify specific genetic variants that influence pharmacokinetics and pharmacodynamics of drugs, better determining their effectiveness/safety profile. Opioid response is a complex scenario, but some gene variants have shown a correlation with pain sensitivity, as well as with opioid metabolism and clinical efficacy/adverse events. Although questions remain unanswered, some of these gene variants may already be used to identify specific patients’ phenotypes that are more prone to experience better clinical response (i.e., better analgesia and/or less adverse events). Once adopted, this approach to opioid prescription may improve a patient’s outcome. This review summarizes the available data on genetic variants and opioid response: we will focus on basic pharmacogenetic and its impact in the clinical scenario discussing how they may lead to more appropriate opioid prescription in cancer patients.

Role of Opioid-Involved Drug Interactions in Chronic Pain Management

The use of opioids for chronic pain management is extraordinarily common despite substantial evidence of only modest benefits, when compared with nonopioid analgesics. Opioid use is also associated with serious risks, including overdose and death. A growing body of evidence suggests that opioids are involved in significant drug interactions that often go unrecognized in clinical practice. Understanding opioid-involved drug interactions is of great practical importance for all health care professionals caring for patients with chronic pain. In this article, we describe the mechanisms of opioid-involved drug interactions and their potential consequences, which have major public health implications. Additionally, this article provides practical strategies to aid health care professionals in avoiding and mitigating opioid-involved drug interactions in order to obtain a favorable balance in the risk-benefit ratio associated with opioid use. These strategies include using osteopathic principles for chronic pain management, separating the times of administration of the opioid(s) from the nonopioid(s) involved in the interaction, changing the opioid(s) adversely affected by the interaction, changing the nonopioid(s) causing the interaction, and partnering with pharmacists in clinical practice.

Is aspirin a substrate of MDR1/P-glycoprotein?

Aspirin (acetyl salicylic acid) is widely used co-medication in patients with cardiovascular and cerebrovascular diseases. Given the prevalence of acetyl salicylic acid's use as a co-medication and conflicting reports in the literature on it being a substrate of P-glycoprotein (P-gp). There is a potential risk for its interaction with compounds with P-gp liability, therefore, we have conducted a detailed investigation to determine substrate potential of acetyl salicylic acid towards P-gp. We observed significantly lower cellular uptake of acetyl salicylic acid in MDR1 transfected LLC-PK1 cells compared to LLC-PK1 wild-type (WT) cells, however, the in vitro efflux of acetyl salicylic acid in MDR1 transfected LLC-PK1 cells was not inhibited by known inhibitors under various conditions. Acetyl salicylic acid did not show active asymmetrical transport across MDR1 transfected LLC-PK1 cells compared to LLC-PK1-WT cells in transwell assay. Moreover, no difference in plasma and brain exposure of acetyl salicylic acid and its metabolite salicylic acid was observed between FVB-WT and Mdr1a/b knockout (KO) mice. Taken together, our findings indicate that acetyl salicylic acid is not a substrate of P-gp.

Impact of Definitive Drug-Drug Interaction Testing on Medication Management and Patient Care

Background and Objective

Aegis Sciences Corporation developed a test (InterACT Rx^™) that objectively and definitively identifies substances known to interact with drug–drug interaction-prone medications commonly prescribed in the treatment of chronic pain and behavioral health disorders. The objective of this study was to assess the severity of identified drug–drug interactions, the reduction in the frequency and severity of identified drug–drug interactions, and the impact of the test on healthcare utilization.

Methods

Patients with chronic pain, behavioral health disorders, or both who had one or more drug–drug interaction tests and one or more drug–drug interactions identified in the study period were included. Drug–drug interaction test results described the number and severity of interactions and detected substances involved in drug–drug interactions. Patients’ electronic medical records were obtained to analyze outpatient visits and prescription medications. The cost of outpatient visits was based on the Medicare Physician Fee Schedule. Outcomes were compared between the pre- and post-study index periods to determine the impact of the drug–drug interaction test on patient care.

Results

A total of 262 patients were included. The majority of drug–drug interactions detected (77.9%) at index were of moderate severity. The number of monthly all-cause and pain-related outpatient visits was reduced in the post-index period compared with the pre-index period (0.74–0.54 and 0.69–0.49, respectively). Associated costs were reduced from US$64.92 to US$51.20, and from US$62.42 to US$47.62, (p < 0.0001 for both) for all-cause and pain-related outpatient visits, respectively. Follow-up drug–drug interaction testing for 43 patients revealed that previously reported drug–drug interactions at the index test were no longer identified in the subsequent test for 39.5% of patients.

Conclusions

Employing a definitive test to detect substances whose interactions may cause adverse drug events can enhance a provider’s insights, drive clinical decision making, and improve patient outcomes.

Electronic supplementary material

The online version of this article (10.1007/s40801-018-0143-z) contains supplementary material, which is available to authorized users.

Characterization of drug-drug interactions in patients whose substance intake was objectively identified by detection in urine

BACKGROUND

Identification of drug-drug interactions (DDIs) typically relies on patient medication lists which are prone to inaccuracies. This study describes use of a mass spectrometry test to detect recently ingested substances in urine with subsequent identification of DDIs.

RESEARCH DESIGN AND METHODS

This was a retrospective analysis of the prevalence of DDIs identified in patients with chronic pain, addiction and/or behavioral health conditions in the U.S. Relationships between patient demographics, polypharmacy and the occurrence of DDIs were also described.

RESULTS

Of 15,004 patients, 2964 (20%) had a DDI identified. There was a positive association between the number of substances detected in urine and the number of interactions identified (r = 0.5033, p-value = 0.0001). Of patients with polypharmacy, 15.6% had contraindicated or severe interactions identified compared to only 3.2% of those without polypharmacy. For polypharmacy patients, the youngest population studied had a much higher likelihood of having one or more DDIs identified compared to the other age groups (p-value = 0.0002).

CONCLUSIONS

By utilizing a mass spectrometry test to objectively detect recently ingested substances followed by identification of DDIs, healthcare providers may be able to better characterize the true incidence of DDIs. Study findings may not be generalizable to healthcare populations outside of pain management, addiction treatment, and behavioral health.

Cytochrome P450 interactions are common and consequential in Massachusetts hospital discharges

Despite the recognition that drug-drug interactions contribute substantially to preventable health-care costs, the prevalence of such interactions related to the cytochrome P450 system in clinical practice remains poorly characterized. This study drew retrospective hospital discharge cohorts from a large health claims data set and a large health system data set. For every hospital discharge, frequency of co-occurrence of substrates and inducers or inhibitors at cytochrome P450 2D6, 2C19, 3A4 and 1A2 were determined. A total of 124 520 individuals in the state of Massachusetts (health claims cohort) and 77 026 individuals in two large academic medical centers (electronic health record (EHR) cohort) were examined. In the claims cohort, 35 157 (28.2%) exhibited at least one CYP450 drug-drug interaction at hospital discharge, whereas in the EHR cohort, 36 750 (47.7%) had at least one interaction. The most commonly affected CYP450 systems were 2C19 and 2D6, with putative interactions observed in at least 10% of individuals at discharge in each cohort. Odds of hospital readmission within 90 days among those discharged with at least one interaction were 10-16% greater, with mean health-care cost $574/month greater over the subsequent year, after adjusting for age, sex, insurance type, total number of medications prescribed, Charlson comorbidity score and presence or absence of a psychiatric diagnosis. These two distinct clinical data types show that CYP450 drug-drug interactions are prevalent and associated with greater probability of early hospital readmission and greater health-care cost, despite the widespread availability and application of drug-drug interaction checking software.

Frequency and clinical relevance of potential cytochrome P450 drug interactions in a psychiatric patient population - an analysis based on German insurance claims data

BACKGROUND

Numerous drugs used in the treatment of psychiatric disorders are substrates of cytochrome P450 enzymes and are potential candidates for drug-drug interactions (DDIs).

METHODS

Claims data of a German statutory health insurance company from severely mentally ill patients who registered in an integrated care contract from August 2004 to December 2009 were analysed. We measured time periods of concomitant prescription of drugs that have been reported to interact via cytochrome P450, with a focus on drugs acting as strong inhibitors. Such drug-drug exposure (DDE) is an incontrovertible precursor of DDIs. We assessed whether potential DDIs were considered clinically relevant based on the prescribing information of the respective drugs.

RESULTS

Among all 1221 patients, 186 patients (15.2 %; Clopper-Pearson 95 % confidence interval (CI): 13.3-17.4 %) had at least one DDE prescription, and 58 patients (4.8 %; 95 % CI 3.6-6.1) had at least one DDE prescription involving a strong cytochrome P450 inhibitor. In 59 patients, (4.8 %; 95 % CI: 3.7-6.2 %) five or more DDEs were identified, and five or more DDEs with a strong inhibitor were identified in 18 patients (1.5 %; 95 % CI: 0.9-2.3). The rates of DDEs were 0.27 (Garwood 95%CI: 0.25-0.28) per person-year and 0.07 (95 % CI: 0.07-0.08) for strong-inhibitor DDEs. Four of the ten most frequent DDEs were identified as clinically relevant, and seven of the eight most frequent DDEs involving a strong inhibitor were clinically relevant.

CONCLUSIONS

The number of patients with DDEs was not alarmingly high in our sample. Nevertheless, prescription information showed that some prescribed drug combinations could result in serious adverse consequences that are known to weaken or strengthen the effect of the drugs and should therefore be avoided.

Drug-Drug Interaction Associated with Mold-Active Triazoles among Hospitalized Patients

The majority of hospitalized patients receiving mold-active triazoles are at risk of drug-drug interactions (DDIs). Efforts are needed to increase awareness of DDIs that pose a serious risk of adverse events. Triazoles remain the most commonly utilized antifungals. Recent developments have included the mold-active triazoles (MATs) itraconazole, voriconazole, and posaconazole, which are first-line agents for the treatment of filamentous fungal infections but have the potential for DDIs. This objective of this study was to evaluate the prevalence of triazole DDIs. Hospitalized U.S. adults with MAT use were identified in the Cerner HealthFacts database, which contained data from over 150 hospitals (2005 to 2013). The severities of DDIs with MATs were categorized, using drug labels and the drug information from the Drugdex system (Thompson Micromedex), into four groups (contraindicated, major, moderate, and minor severity). DDIs of minor severity were not counted. A DDI event was considered to have occurred if the following two conditions were met: (i) the patient used at least one drug with a classification of at least a moderate interaction with the MAT during the hospitalization and (ii) there was a period of overlap between the administration of the MAT and that of the interacting drug of at least 1 day. A total of 6,962 hospitalizations with MAT use were identified. Among them, 88% of hospitalizations with voriconazole use, 86% of hospitalizations with itraconazole use, and 93% of hospitalizations with posaconazole use included the use of a concomitant interacting drug. A total of 68% of hospitalizations with posaconazole use, 34% of hospitalizations with itraconazole use, and 20% of hospitalizations with voriconazole use included the use of at least one drug with a DDI of contraindicated severity. A total of 83% of hospitalizations with posaconazole use, 61% of hospitalizations with itraconazole use, and 82% of hospitalizations with voriconazole use included the use of at least one drug that resulted in a severe DDI. The findings of this study demonstrate that a majority of hospitalized patients receiving MAT are at risk for severe drug-drug interactions and highlight the need for antifungal stewardship.

A retrospective, matched cohort study of potential drug-drug interaction prevalence and opioid utilization in a diabetic peripheral neuropathy population initiated on pregabalin or duloxetine

Background

Anticipating and controlling drug-drug interactions (DDIs) in older patients with painful diabetic peripheral neuropaty (pDPN) presents a significant challenge to providers. The purpose of this study was to examine the impact of newly initiated pregabalin or duloxetine treatment on Medicare Advantage Prescription Drug (MAPD) plan pDPN patients’ encounters with potential drug-drug interactions, the healthcare cost and utilization consequences of those interactions, and opioid utilization.

Methods

Study subjects required a pregabalin or duloxetine pharmacy claim between 07/01/2008-06/30/2012 (index event), ≥1 inpatient or ≥2 outpatient medical claims with pDPN diagnosis between 01/01/2008-12/31/2012, and ≥12 months pre- and ≥6 post-index enrollment. Propensity score matching was used to balance the pregabalin and duloxetine cohorts on pre-index demographics and comorbidities. Potential DDIs were defined by Micromedex 2.0 and identified by prescription claims. Six-month post-index healthcare utilization (HCU) and costs were calculated using pharmacy and medical claims.

Results

No significant differences in pre-index demographics or comorbidities were found between pregabalin subjects (n = 446) and duloxetine subjects (n = 446). Potential DDI prevalence was significantly greater (p < 0.0001) among duoxetine subjects (56.7%) than among pregabalin subjects (2.9%). There were no significant differences in HCU or costs between pregablin subjects with and without a potential DDI. By contrast, duloxetine subjects with a potential DDI had higher mean all-cause costs ($13,908 vs. $9,830; p = 0.001), more subjects with ≥1 inpatient visits (35.6% vs 25.4%; p = 0.02), and more subjects with ≥1 emergency room visits (32.8% vs. 20.7%; p = 0.005) in comparison to duloxetine subjects without a potential DDI. There was a trend toward a difference between pregabalin and duloxetine subjects in their respective pre-versus-post differences in milligrams (mg) of morphine equivalents/30 days used (60.2 mg and 176.9 mg, respectively; p = 0.058).

Conclusion

The significantly higher prevalence of potential DDIs and potential cost impact found in pDPN duloxetine users, relative to pregabalin users, underscore the importance of considering DDIs when selecting a treatment.

Impact of potential pregabalin or duloxetine drug-drug interactions on health care costs and utilization among Medicare members with fibromyalgia

PURPOSE

To examine the impact of newly initiated pregabalin or duloxetine treatment on fibromyalgia (FM) patients' encounters with potential drug-drug interactions (DDIs), the health care cost and utilization consequences of those interactions, and the impact of treatment on opioid utilization.

PATIENTS AND METHODS

Subjects included those with an FM diagnosis, a pregabalin or duloxetine prescription claim (index event), ≥1 inpatient or ≥2 outpatient medical claims, and ≥12 months preindex and ≥6 postindex enrollment. Propensity score matching was used to help balance the pregabalin and duloxetine cohorts on baseline demographics and comorbidities. Potential DDIs were defined based on Micromedex 2.0 software and were identified by prescription claims.

RESULTS

No significant differences in baseline characteristics were found between matched pregabalin (n=794) and duloxetine cohorts (n=794). Potential DDI prevalence was significantly greater (P<0.0001) among duloxetine subjects (71.9%) than among pregabalin subjects (4.0%). There were no significant differences in all-cause health care utilization or costs between pregabalin subjects with and without a potential DDI. By contrast, duloxetine subjects with a potential DDI had higher mean all-cause costs ($9,373 versus $7,228; P<0.0001) and higher mean number of outpatient visits/member (16.0 versus 13.0; P=0.0009) in comparison to duloxetine subjects without a potential DDI. There was a trend toward a statistically significant difference between pregabalin and duloxetine subjects in their respective pre- versus post-differences in use of ≥1 long-acting opioids (1.6% and 3.4%, respectively; P=0.077).

CONCLUSION

The significantly higher prevalence of potential DDIs and potential cost impact found in FM duloxetine subjects, relative to pregabalin subjects, underscore the importance of considering DDIs when selecting a treatment.

Cost comparison of drug-drug and drug-condition interactions in patients with painful diabetic peripheral neuropathy treated with pregabalin versus duloxetine

PURPOSE

The frequency and financial impact of potential drug-drug interactions (DDIs) and drug-condition interactions (DCIs) in patients with painful diabetic peripheral neuropathy (DPN) treated with either pregabalin or duloxetine were compared.

METHODS

This retrospective cohort study was conducted using a large U.S. administrative claims database. Patients selected for study inclusion had a diagnosis of DPN and were newly initiated on either pregabalin or duloxetine between July 1, 2008, and October 1, 2010. Data on potential DDIs and DCIs were collected. Health care costs were measured as the sum of gross covered payments for all medical and prescription claims incurred during the six months after the index date.

RESULTS

The study sample comprised 2499 pregabalin users and 1354 duloxetine users. Among pregabalin users, 48 (1.8%) had at least one potential pregabalin DCI; none had potential pregabalin DDIs. Among duloxetine users, 966 (71%) had at least one potential duloxetine DDI or DCI. The frequencies of potential DDIs and DCIs differed significantly between pregabalin and duloxetine users (p < 0.001). Potential duloxetine DDIs and DCIs were associated with a significant increase in mean health care costs in duloxetine users (p = 0.002). Potential pregabalin DDIs and DCIs were not associated with additional health care costs in pregabalin users.

CONCLUSION

Among patients with painful DPN treated with either pregabalin or duloxetine, the frequency of potential duloxetine DDIs and DCIs was substantially higher than that of pregabalin. Potential DDIs and DCIs were associated with significantly increased health care costs in duloxetine users.

Economic implications of potential drug-drug interactions in chronic pain patients

Chronic pain patients may be subject to polypharmacy because of long-term pharmacological pain treatment and additional comorbidities. Many chronic pain patients expose themselves to potential drug-drug interactions (DDIs) and these interactions can have unintended and severe consequences. Prevalence and costs associated with DDIs are inconsistent and has led to an inadequate level of awareness among the medical community; therefore, it has become necessary to re-evaluate the rates of DDIs in chronic pain patients. Utilizing medical and prescription claims databases, five studies were conducted to assess the health care utilization of and associated financial payments for patients >18 years with chronic noncancer pain. The studies evaluated drug-drug exposures with the potential to cause DDIs specifically occurring through the CYP450 enzyme system. The studies reported that drug-drug exposures are prevalent, costly and can occur in any age group and that physicians should consider ways to limit their patients' exposure to potential DDIs.

Drug-drug interaction between NSAIDS and low-dose aspirin: a focus on cardiovascular and GI toxicity

INTRODUCTION

The aging of the population in the US and other countries means that a large number of people will likely take NSAIDs for the relief of pain and low-dose aspirin (LD-ASA) for cardioprotection. However, the cardioprotective value of LD-ASA can be compromised in patients who take NSAIDs concomitantly, because some NSAIDs competitively bind to critical amino-acid residues on cyclooxygenase (COX) enzymes and interfere with the mechanism of antiplatelet activity of LD-ASA.

AREAS COVERED

A review of the literature was conducted to provide an overview of current issues surrounding the concomitant use of NSAIDs and LD-ASA, to explore potential mechanisms for this drug-drug interaction and to consider current and future treatment options that may mitigate the risk associated with their concomitant use.

EXPERT OPINION

NSAIDs offer effective pain relief for the most common forms of pain, such as low back pain, musculoskeletal pain associated with arthritis, postsurgical pain, headache, acute pain syndromes, menstrual pain and dental pain. The development of NSAID formulations that offer effective pain control with fewer or less serious adverse effects due to interference with ASA would be a valuable medical advance. Several promising treatment options and regimens may be available in the future.

Potential drug-drug and drug-condition interactions among fibromyalgia patients initiating pregabalin or duloxetine: prevalence and health care expenditure impact

OBJECTIVE

To quantify the prevalence of potential drug-drug/drug-condition interactions (DDI/DCI) among fibromyalgia patients initiating pregabalin or duloxetine, and to determine the impact of potential DDI/DCI on health care expenditures.

DESIGN

Retrospective cohort study.

SETTING

U.S. clinical practice, as reflected within a large administrative claims database.

SUBJECTS

Fibromyalgia patients newly initiating pregabalin or duloxetine between July 1, 2008 and October 1, 2010 (initiation date = index).

OUTCOME MEASURES

Potential DDI measured using clinical software that identifies co-prescription of medications that potentially interact with pregabalin or duloxetine. Potential DCI, drawn from the contraindications and warnings and precautions sections of pregabalin and duloxetine prescribing information, measured using administrative claims-based algorithms. All-cause health care expenditures measured throughout a 6-month postindex period. Analyses included univariate, bivariate, and multivariable statistical approaches.

RESULTS

Seven thousand seven hundred fifty-one pregabalin and 7,785 duloxetine initiators were selected for study: mean age 49 years, 88% female. Only 1.4% of pregabalin initiators had ≥1 potential pregabalin DCI; none had potential pregabalin DDI. In contrast, 67% of duloxetine initiators had potential duloxetine DDI/DCI, driven mostly by potential duloxetine DDI (62% of duloxetine initiators). Compared between pregabalin and duloxetine initiators, differences in the prevalence of potential DDI/DCI were statistically significant (P < 0.001). Multivariable analyses indicated that, among duloxetine initiators, those with potential duloxetine DDI/DCI had postinitiation health care expenditures that were $670 higher (P < 0.001) than those without potential duloxetine DDI/DCI. Among pregabalin initiators, potential pregabalin DDI/DCI were not associated with health care expenditures.

CONCLUSIONS

Among fibromyalgia patients initiating pregabalin or duloxetine, potential duloxetine DDI could be highly prevalent. Among duloxetine initiators, potential duloxetine DDI/DCI were significantly associated with increased health care expenditures.

Opioid therapy pharmacogenomics for noncancer pain: efficacy, adverse events, and costs

Chronic non-cancer pain is a debilitating condition associated with high individual and societal costs. While opioid treatment for pain has been available for centuries, it is associated with high variability in outcome, and a considerable proportion of patients is unable to attain relief from symptoms while suffering adverse events and developing medication dependence. We performed a review of the efficacy of pharmacogenomic markers and their abilities to predict adverse events, dependence, and associated economic costs, focusing on two genes: OPRM1 and CYP2D6. Data sources were articles indexed by PubMed on or before August 6, 2013. Articles were first selected after review of their titles and abstracts, and full papers were read to confirm eligibility. Initially, fifty-two articles were identified. Of these, 17 were relevant to biological actions of pharmacogenomic markers and their effect on therapeutic efficacy, 16 to adverse events, 15 to opioid dependence, and eight to economic costs. In conclusion, increasing costs of opioid therapy have made the advances in pharmacogenomics an attractive solution to personalize care with unclear repercussions related to the impact on costs, morbidity, and outcomes. This intersection of pharmacoeconomics and pharmacogenomics presents a unique platform to further examine current advances in clinical medicine and their utility in cost-effective treatment of chronic pain.

Recent Publications on Medications and Pharmacy

Hospital Pharmacy presents this feature to keep pharmacists abreast of new publications in the medical/pharmacy literature. Articles of interest regarding a broad scope of topics are abstracted monthly. Suggestions or comments may be addressed to Flint Russett, St. Claire Regional Medical Center, 222 Medical Circle, Morehead, KY 40351, or e-mail: FSRussett@st-claire.org .